JPS6316247B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for producing thermoplastic material supplied in particulate form to be filled with reinforcement using a screw extruder in which the material is melted. and in which the reinforcing material is fed with additional particles to the mixing zone of the extrusion device containing the dissolved material.

According to a method already known from DE-OS 2601696, a thermoplastic material is fed in particulate form to the inlet of a screw extruder, is melted in the melting zone of the extruder, and reinforcing material is added in the mixing zone. is added. For this purpose, an injection channel is provided at the beginning of the mixing zone for the reinforcing material, which is mixed along the mixing zone with the molten thermoplastic material for homogenization of the material.

According to DE-OS 2614136, in the case of a two-screw extrusion device, more reinforcement injection channels can also be provided in the mixing region.

Due to the mixing of the reinforcement, a certain length of the extruder is required in order to achieve the desired homogeneity of the material, such known methods require a considerable amount of molten thermoplastic material. The undesirable result of having to transport the material over a length of mixing region is often an adverse effect of the properties of thermoplastic materials. For these reasons, screw extruders of this type have relatively low rotational speeds or have cooling in the mixing zone in order to prevent prolonged overheating of the thermoplastic material.

In order to prevent such undesirable effects, the literature "PLASTVERARBEITER" Volume 3 (1980)
In connection with the use of glass fibers as reinforcement, a method is proposed in which they are fed together with additional particles into a screw extruder from the beginning of the mixing zone. There is. The addition of additional particles serves to provide cooling of the molten thermoplastic material contained in the mixing zone and to counteract the effects of prolonged exposure of the material to high temperatures. But first of all, in the injection channel for the glass fibers and the additional particles, the friction between these substances becomes large, leading to extensive destruction of the glass fibers,
In each case, undesired shortening of the glass fibers occurs. In addition to this, this also causes significant wear on the walls of the injection channel.

Additionally, DE-OS 1927271 describes the use of a narrow melt zone in the mixing zone of a melt extruder to incorporate glass fibers, particularly in the form of endless filaments, into thermoplastic materials. A method of mixing additional particles with separate glass fibers is described. This separate feeding technique serves the purpose of taking advantage of the effect of breaking up larger additional particles into smaller pieces as they pass through the unmelted additional particles to the mixer. Note that this viscous mixing device is provided behind the glass fiber supply section. This is also because the additional particles form dry clumps that break up the glass fibers so strongly that they make up a large portion of the undesirable fines, which makes the final product brittle. This is because it will happen.

The present invention is directed to the mixing of thermoplastic materials while preventing such atomizing effect of additional particles and thereby protecting the reinforcement. According to the invention, the additional particles are mixed with the melt by means of a mixing or viscous mixing element provided between the additional particles and the reinforcing material injection path, and are thus superficially melted, so that the reinforcing material In the feed region, the additional particles are retained in the melt in solid state without being substantially melted.

Apart from DE-OS1927271 mentioned above, this also includes a mixing or viscous mixing element between the supply of additional particle reinforcement so that the additional particles are spread homogeneously into the melt before the supply of reinforcement. Devices are known in which the melt is brought into contact with additional particles at the feed of the reinforcing material, and the reinforcing material is introduced into the melt in a particularly protected manner. mixed together. The reason is that the additional particles are somewhat melted on the surface at this location, but are in a solid state internally, so mixing of the reinforcing material takes place through the additional particles, and it softens homogeneously. In addition, the surface of the additional particles is subjected to only a slight bending or shearing force until melting, thus eliminating the strong pulverizing action of the additional particles, as in the known device. It is. Due to the envelopment of the additional particles, the reinforcement is not exposed to dry friction by the molten material, since the melt surrounding the additional particles has a lubricating effect on the reinforcement; also has a protective effect, yet the strong mixing effect of the additional particles is maintained.
Furthermore, a desirable cooling effect of the molten material is provided so that it is not exposed to large thermal loads. The additional particles can be made of the same plastic material or can be other materials suitable for co-addition.

A suitable amount of additional particles for this purpose is 10 to 60%, preferably 30 to 50% of the total particle amount.

Glass fibers or carbon fibers, in particular, are used as reinforcement material in advance of any fibers.

The invention furthermore relates to a screw extruder embodying the method described above, in which the injection channel is divided into multiple parts along the axis of the extrusion device in a known manner. This kind of screw type extruder is
It is shown in DE-OS2614136 mentioned above.

In the screw type extruder based on this invention,
An injection path for supplying the additional particles is provided at the beginning of the mixing zone, and an injection path for the reinforcement is provided immediately adjacent to the supply path for the additional particles, so that the additional particles enter the melt without substantially melting. The screws are separated between the two injection channels by a mixing or viscous mixing element.

Both injection channels are also located relatively close to each other, so that additional particles are transported by the screw extrusion device into the region of the reinforcement injection channel.
It is incorporated into the melt virtually without melting, and the mixing effect is carried out by means of a mixing or viscous mixing element located between the two injection channels.

The screw extruder used for carrying out the method according to the invention is configured as a single-screw extrusion device or a double-screw extrusion device.

To this end, the diameter of the screw in the melting zone located in the mixing zone is smaller than in the mixing zone, and the rotational speed of the screw is greater in the melting zone than in the mixing zone. Because of this, due to the passage of reinforcement as well as additional particles,
The free cross section is enlarged in the mixed region. In this way, no backwash occurs in this injection channel.

The screw extruder shown in FIG. 1 consists of a housing 1 into which a screw 2 having both volutes 3 and 4 is inserted. The screw 2 is divided into regions of different core diameters, region 5 having a smaller core diameter than the next region 6. Regions 7 and 9 again have the same core diameter as region 5, whereas regions 8 and 10 have the same large core diameter as region 6. In the regions with small core diameters, namely regions 5, 7 and 9, there is material in the screw extruder; in region 5 there is no injection channel 1.
1. In this case, the problem here is the thermoplastic material 33 shown in granular form, which is transported from region 5 to region 6 and is subjected to a strong shearing force due to its increasing core diameter. It receives and melts. Regions 5 and 6 thus form fused regions. There will then be molten plastic material in the following region 7. Additional particles 34 are fed into this region via the injection channel 12, where they are mixed with the molten thermoplastic material 33 without backwashing, due to the reduced core diameter of the screw 2. The following region 8 is provided with projections 13 which act as mixing or kneading elements.
Here, a strong mixing effect is also exerted due to the increased core diameter there, and the injection channel 12
The additional particles 34 fed in are thus successfully mixed with the molten thermoplastic material 33. The following region 9 has a further injection channel 14 through which the reinforcing material 3 is introduced into the material conveyed into the extruder.
5. For example, glass fibers are supplied. Here again, no backwash occurs in the injection channel 14 due to the small diameter of the core. Next, the following area 10
The molten thermoplastic material 33, the additional particles 34 and the reinforcing material 35 are mixed at , whereby the additional particles 34 are also melted and a significant amount of heat is removed from the already molten thermoplastic material 33. The material is not exposed to large heat loads. In the above, areas 7, 8, 9
and 10 constitute a mixed area.

The final mixture of thermoplastic and reinforcement material is then passed through a nozzle plate 15 having nozzles 16.
It is squeezed out even more.

The additional particles 34 supplied from the injection channel 12 in the region 7 are not subjected to particularly large pressures in that region, first of all because the core diameter of the screw 2 is designed to be small there. Subsequently, in region 8, melted thermoplastic material 33 is applied.
A mixing of the additional particles 34 takes place with the addition particles 34, but in particular there, due to the short area, the additional particles 34 are virtually undissolved and the area to which the reinforcing material 35 is supplied via the injection channel 14. Go straight into 9. In this region 9 the core diameter is again becoming smaller, so that the material there is first of all transported virtually without pressure until it reaches the last longer region 10 with a larger core diameter, where it , due to the given length and larger core diameter, intense thorough mixing takes place, but the reinforcement 35 is well protected. Since it is already surrounded by the molten thermoplastic material 33, it does not come into direct contact with the additional particles that are still present in this form, which ensures a reliable lubricating effect with respect to the reinforcement 35. It means fulfilling.

The screw type extruder shown in FIG. 2 is a double screw type extruder, with only one screw 17 clearly shown. Screw 17 is housing 2
However, the diameter of the housing 22 is smaller than that of the housing 23. Correspondingly, the end of the screw passing through the housing 22 has a smaller outer diameter than the end of the screw passing through the housing 23.

A particulate thermoplastic material 33 is fed to the double screw extruder through an injection channel 24;
It is melted in the melting zone 18. This melting zone 18 is provided with viscous mixing elements 25 and 26 to assist in melting. Connected to region 18 are regions 19, 20 and 21, in which the outer diameter of the screw is larger than in melting region 18. At the same time, the screw 17 is more
It has a higher rotational speed in the melting region 18. By doing so, a larger free cross section is provided in the mixing region than in the melting region 18, and the mixing region 19, 20, 2
1 with additional particles 34 as well as reinforcement 35
can also be mixed without the risk of spoilage.

Additional particles 34 are added to region 19 through injection channel 27.
is supplied and mixed into the molten hot plastic material in region 20 by a mixing element 28 provided therein. This is followed by the incorporation of reinforcing material, for example glass fibers, through the injection channel 29, which is heated by the melting heat along the region 21 under the action of the additional particles 34 which are still present in this form adjacent to the region 21. The plastic material 33 is mixed, the mixing action being facilitated by the mixing elements 30 and 31. A complete dissolution of the additional particles 34 and with it a mixing of the reinforcing material 35 takes place in the relatively long region 21, which brings the additional particles 34 into dry frictional contact with the reinforcing material 34. is treated in a protected manner. The homogenized material produced in this way is
It then exits the double screw extruder at the end of zone 21.

The extruder according to FIG. 2 is additionally provided with an exhaust gas opening 36 which is provided in a known manner so that the generated gas can be freely removed.

In FIGS. 3 and 4, the known construction of a double-screw extruder is shown in cross-section. Here, FIG. 3 shows a cross section taken along line AA in FIG. 2. As is clear from the figure, two three-thread screws are shown here.

FIG. 4 shows a cross section along the line B--B in FIG. 2, in which both screws 17 and 32 are constructed in the form of two threads. Both screws 17 and 32 pass through each other and have the same axial distance a.

[Brief explanation of the drawing]

FIG. 1 shows a single screw extruder. FIG. 2 shows a double screw extruder with stepped screw diameters. Figure 3 shows the line A- in Figure 2.
A cross-sectional view along line A is shown. FIG. 4 shows a cross-sectional view along the line B--B of FIG. In the figure, 1 is a housing, 2 is a screw, 3 and 4 are spirals, 33 is a thermoplastic material, 12 is an injection path, and 34 is an additional particle 35 is a reinforcing material.

Claims (1)

[Scope of Claims] 1. A method for producing a thermoplastic material supplied in particulate form to be filled with a reinforcing material using a screw extruder for melting the material, the method comprising: , in the mixing zone of the melt extrusion device, the additional particles and subsequently the reinforcing material are fed separately therefrom, the additional particles 34 being fed into the supply of the additional particles 34 and the reinforcing material 35. Additional particles 34 are added in the feed area of the reinforcing material 35 in such a way that they are mixed with the melt by the mixing elements 12, 14 and the viscosity mixing elements 13, 28, and are very widely dissolved on the surface. A method for producing a thermoplastic material, characterized in that it remains in a solid state in a melt without being substantially melted. 2. characterized in that the additional particles are 10 to 60%, preferably 30 to 50% of the total particle amount;
A method according to claim 1. 3. Method according to claim 1 or 2, characterized in that fibers, in particular glass or carbon fibers, are used as reinforcement 35. 4. Claim 1 or 2, characterized in that a glass bulb is used as the reinforcing material 35.
The method described in section. 5. Screw-type extruder for producing thermoplastic materials filled with reinforcement, with a number of injection channels 12, 27 divided along the axis of the extruder.
an injection path 12, 27 for the additional particles 34 at the beginning of the mixing region 7, 8, 9, 10; 19, 20, 21, and an injection path 14, for the reinforcement 35; 29 is injection path 1 for additional particles 34
Additional particles 34 due to close proximity after 2,27
is embedded in the melt virtually without melting, the screw 2; 17, 32 being interrupted between the two injection channels 12, 27; 14, 29 by a mixing or viscous mixing element 13, 28. A screw type extruder that is characterized by: 6. The screw type extruder according to claim 5, characterized in that it is composed of one screw extrusion member 2. 7. The screw type extruder according to claim 5, characterized in that it is composed of double screw extrusion members 17 and 32. 8 The screw diameter in the melting zone 18 preceding the mixing zone 19, 20, 21 is equal to that of the mixing zone 1.
9, 20, 21, and the screws 17, 32 in the melting zone 18 have a higher rotational speed than in the mixing zone 19, 20, 21. screw type extruder.